Lightweight implantable prosthetic device

ABSTRACT

A reduced weight implantable prosthesis, including, an outer surface shell for encapsulating the prosthesis, a gel mixture comprising a mixture of a cohesive gel and micro-spheres for filling the shell, one or more inner volumes internal to the shell which do not contain the gel mixture; and wherein the gel mixture contains less than 60% by volume of micro-spheres mixed into the cohesive gel.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase application of PCTInternational Application No. PCT/IL2006/000501, filed on 24 Apr. 2006,which claims the benefit of U.S. Provisional Application Ser. No.60/674,336, filed on 25 Apr. 2005, and U.S. Provisional Application Ser.No. 60/698,973, filed on 14 Jul. 2005, all of which are herebyincorporated by reference in their entirety.

RELATED APPLICATIONS

The current application claims priority from U.S. provisionalapplication No. 60/674,336 titled “implantable prosthetic device andmethod of usage of the same” filed Apr. 25, 2005, and U.S. provisionalapplication No. 60/698,973 titled “implantable prosthetic device andmethod of usage of the same” filed Jul. 27, 2005, the disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to implantable prostheticdevices and specifically to implantable prosthetic devices of reducedweight.

BACKGROUND OF THE INVENTION

In the last century reconstructive and cosmetic surgery has become acommon practice. Specifically cosmetic breast surgery has been developedto allow reconstruction of a woman's breast that was affected byprocedures such as mastectomy. Cosmetic breast surgery has also becomeavailable to amend the appearance of a woman's breast, for example byadding an implant to increase the size of the breast, to correctasymmetries, change shape and fix deformities.

Generally the implant is required to be able to provide a specific formand maintain the form for many years, preferably for the lifetime of thewoman in which the implant is installed to prevent the need foradditional invasive surgery. The implant is also required to have aspecific feel preferably imitating the feel of a real breast. Theimplant also needs to be bio-durable such that it is not ruined byinteraction with the human body and it needs to be bio-compatible sothat the woman's health is not detrimentally affected by the implanteven under extreme circumstances, for example the implant is required tobe non toxic in case of leakage from the implant.

The standard implants used today comprise an outer shell typicallyformed from vulcanized silicone or polyurethane, and an inner contenttypically formed from a silicone gel or saline. The specific weight ofthe commonly used filling materials is generally between 0.95 to 1.15(grams per centimeter cube). An average implant may weigh between 50 to1000 grams, or even more. The weight of the implant is an addition,which is not negligible for a person.

Over time breast implants are known to cause many problems, mostlyrelated to the weight of the implant, for example: ptosis (i.e. saggingand deformity), breast tissue atrophy, prominence of the implant throughbreast tissue, back pain, and striae of the skin.

Traditionally, the silicone gels used had silicone oils with shortpolymers in them that leached out through the shell over time. Currentimplants involve the use of a shell with barrier layers to achieve verylow permeability, and using a cohesive gel as the filling material. Thecohesiveness ensures that the filling material does not leak out intothe body, even in case of rupture of the shell.

An additional characteristic to be considered in selection of thefilling material is the resilience, elasticity and pliability of theimplant, which provides it with a specific feeling when being sensed.Generally it is desirable to provide an implant which provides aspecific shape and mimics the feel of real human tissue at the positionof the implant. It is important that the implant maintain its form andfeel for extended periods, to prevent the need for additional surgery.

US patent application publication no. 2004/0153151 to Gonzales datedAug. 5, 2004 of which the disclosure is incorporated herein by referencedescribes a breast prosthesis from silicone that is formed as atrabecular body or micro-cell body in order to obtain a prosthesis oflower density.

U.S. Pat. No. 4,380,569 to Shaw dated Apr. 19, 1983 of which thedisclosure is incorporated herein by reference, describes a reducedweight breast prosthesis which is worn external to the human body orimplanted into the human body. The breast prosthesis is comprised from amixture of a silicone gel with glass micro-spheres.

U.S. Pat. No. 5,902,335 to Snyder, Jr. dated May 11, 1999 of which thedisclosure is incorporated herein by reference, describes a reducedweight breast prosthesis which is worn external to the human body, basedon the U.S. Pat. No. 4,380,569 to Shaw. Snyder states that the use ofglass micro-spheres as described by Shaw results in a stiff product thatdoes not mimic the human breast as well as silicone gel alone. Snyderdescribes a breast prosthesis having two sections. A first outer sectionfilled with silicone gel that mimics the human breast and a second innersection of reduced weight to reduce the weight of the prosthesis.

U.S. Pat. No. 5,658,330,to Carlisle et al. dated Aug. 19, 1997 of whichthe disclosure is incorporated herein by reference, describes a moldedsilicone foam implant and method for making it.

SUMMARY OF THE INVENTION

An aspect of an embodiment of the invention relates to a reduced weightimplantable prosthesis filled with a inner content that mimics theresilience and feel of real human tissue, for example, a reduced weightbreast implant that mimics the resilience and feel of breast tissue. Thespecific gravity of the prosthesis of this invention can be reduced toas little as 0.3 g/cc or less. The weight reduction is achieved bycreating one or more areas in the prosthesis that are void of siliconegel, and by using a reduced weight gel mixture to replace heaviersilicone gels that are commonly used.

In an exemplary embodiment of the invention, the inner content iscomprised of a filler material that is a gel mixture and comprises acohesive silicone gel mixed with multiple particles such asmicro-spheres. The multiple particles can be of varying sizes, textures,weight, shape, materials, permeability, specific gravity and may be inthemselves comprised of multiple particles. In an exemplary embodimentof the invention, the inner content is encased in a low penetratableouter surface that is optionally, comprised from a biocompatiblesilicone or other material. The outer surface serves as an enclosure forholding the reduced weight inner content. In an exemplary embodiment ofthe invention, the micro-spheres used in the gel mixture have a diameterof less than 200 microns, for example between 30-40 microns. Optionally,up to 60% of the gel mixture by volume comprises micro-spheres. In someembodiments of the invention, micro-spheres of larger diameter are usedfor preparing a gel mixture. Optionally, a mixture with largermicro-spheres (e.g. with a diameter of up to 500 microns or even up to1000 microns) has a lower specific gravity than a mixture with smallermicro-spheres with similar wall thickness. In some embodiments of theinvention, the prosthesis' inner content may be divided to multipleareas and different areas may utilize different filler materialincluding different gel mixtures with a different specific gravity andpossibly a different feel.

In an exemplary embodiment of the invention, an inner volume of theprosthesis is replaced with a filler material that is lighter than thegel mixture which is used to fill the rest of the prosthesis.Optionally, the gel mixture serves as padding surrounding the replacedinner volume to mimic the resilience and feel of real breast tissue,although the inner volume may not be as resilient as the gel mixture. Inan exemplary embodiment of the invention, the resulting prosthesisachieves a weight reduction of up to 35%-70% or more. In someembodiments of the invention, the weight reduction of the prosthesis isachieved by providing a prosthesis with an inner volume filled with afoamy or sponge like silicone body surrounded by the gel mixturecomprised from a mixture of a silicone gel and hollow micro-spheres.Optionally, the inner volume is encased in a low penetratable enclosurethat is optionally, comprised from a biocompatible silicone. Optionally,the enclosure can be smooth or textured, with a round or anatomical orother shape.

In some embodiments of the invention, the inner volume is completelysurrounded by the gel mixture to provide the required resilience.Alternatively, the inner volume is connected to one side of the outersurface, for example the side which does not face the surface skin ofthe person in order for the gel mixture to be sensed by external sensingand to reduce contact of the inner volume with external sensors.Optionally, the gel surrounding the spongy like body screens it andprovides the required feel.

In an exemplary embodiment of the invention, the sponge like siliconebody has a specific gravity, which is approximately 30-40% of thespecific gravity of silicone gel, for example 0.35 g/cc. Optionally, thegel mixture described in the current application has a specific gravityin the range of 45%-75% of the specific gravity of a silicone gelwithout micro-spheres mixed in. In an exemplary embodiment of theinvention, the micro-spheres have a specific gravity which isapproximately between 10-40% of the specific gravity of silicone gel,for example between 0.1 g/cc to 0.4 g/cc.

In an exemplary embodiment of the invention, the inner volume may befilled with a gel mixture with larger micro spheres that has a lowerspecific gravity value than the gel mixture used to pad the innervolume.

In an exemplary embodiment of the invention, the reduced weightprosthesis may be provided in various sizes, for example extending from50 CC to 1500 CC or larger or smaller. Optionally, a reduced weightprosthesis may be implanted in other areas of the body other than thebreast, for example to replace or augment testicles, pectorals, a chin,cheeks, a calf, buttocks or other parts of the human or an animal body,while exhibiting tactile properties similar to natural tissue.

In some embodiments of the invention, the methods described above may beused to form an external prosthesis, which is worn external to the bodyunder or as part of a person's clothes.

In some embodiments of the invention, the methods described above may beused as part of an implantable device or apparatus such as a cardiacpacemaker.

There is thus provided in accordance to an exemplary embodiment of theinvention, a reduced weight implantable prosthesis, including, an outersurface shell for encapsulating the prosthesis, a gel mixture comprisinga mixture of a cohesive gel and micro-spheres for filling the shell, oneor more inner volumes internal to the shell which do not contain the gelmixture; and wherein the gel mixture contains less than 60% by volume ofmicro-spheres mixed into the cohesive gel. In an exemplary embodiment ofthe invention, the total volume of the one or more inner volumes is lessthan half of the volume of the prosthesis. Optionally, the total volumeof the one or more inner volumes is less than a third of the volume ofthe prosthesis. In an exemplary embodiment of the invention, the totalvolume of the one or more inner volumes is greater than a quarter of thevolume of the prosthesis. Optionally, the content of the one or moreinner volumes has a specific gravity that is less than the specificgravity of the mixture.

In an exemplary embodiment of the invention, the content of at least oneof the one or more inner volumes is a foamy silicone substance.Optionally, the content of at least one of the one or more inner volumeis a silicone formed with a trabecular or micro-cell structure. In anexemplary embodiment of the invention, at least one of the one or moreinner volumes comprise a silicone shell supported by a mechanicalstructure formed from silicone rods. Optionally, at least one of the oneor more inner volumes comprise a self supporting hollow silicone shell.

In an exemplary embodiment of the invention, the one or more innervolumes are surrounded by the gel mixture. Optionally, at least one ofthe one or more inner volumes is approximately centered in the outersurface shell. In an exemplary embodiment of the invention, at least oneof the one or more inner volumes is positioned adjacent to one side ofthe outer surface shell. Optionally, at least one of the one or moreinner volumes is filled with a gel mixture with micro-spheres that havea larger diameter than the micro-spheres in the gel mixture external tothe inner shell. In an exemplary embodiment of the invention, at leastone of the inner volumes is subdivided to an internal outer layer and aninternal inner volume. Optionally, the subdivided inner volume comprisescontent of different specific gravity values in the differentsubdivisions of the inner volume.

In an exemplary embodiment of the invention, the micro-spheres arehollow. Optionally, the gel mixture comprises micro-spheres of more thanone size. In an exemplary embodiment of the invention, the micro-spheresare non-spherical. Optionally, the outer surface shell is formed from alow penetratable material. In an exemplary embodiment of the invention,the gel mixture masks the feel of the content of the one or more innervolumes. Optionally, the content of at least one of the one or moreinner volumes comprises a gel mixture with micro-spheres of more thanone size.

In an exemplary embodiment of the invention, the outer surface shell hasa smooth outer surface. Alternatively, the outer surface shell has atextured outer surface. In an exemplary embodiment of the invention, theouter surface shell is round in shape. Optionally, the outer surfaceshell is anatomical in shape.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description taken in conjunction with theattached drawings. Identical structures, elements or parts, which appearin more than one figure, are generally labeled with a same or similarnumber in all the figures in which they appear, wherein:

FIG. 1 is a schematic illustration of an implantable prosthesis filledwith a gel mixture, according to an exemplary embodiment of theinvention;

FIG. 2A is a schematic illustration of a prosthesis with a centeredinner volume with a first filler material and an outer volume encasingthe inner volume with a second filler material, according to anexemplary embodiment of the invention;

FIG. 2B is a schematic illustration of a prosthesis with a non-centeredinner volume with a first filler material and an outer volume encasingthe inner volume with a second filler material, according to anexemplary embodiment of the invention;

FIG. 3A is a schematic illustration of an inner volume with a foamy likestructure, according to an exemplary embodiment of the invention;

FIG. 3B is a schematic illustration of an inner volume with acompartment like structure, according to an exemplary embodiment of theinvention;

FIG. 3C is a schematic illustration of an inner volume with a threedimensional mechanical rod like structure, according to an exemplaryembodiment of the invention;

FIG. 3D is a schematic illustration of an inner volume with a selfsupporting surface structure, according to an exemplary embodiment ofthe invention;

FIG. 4A is a schematic illustration of a concentric multilayeredprosthesis, according to an exemplary embodiment of the invention; and

FIG. 4B is a schematic illustration of a prosthesis with multiple innervolumes, according to an exemplary embodiment of the invention

DETAILED DESCRIPTION

FIG. 1 is a schematic illustration of an implantable prosthesis 100filled with a gel mixture 120, according to an exemplary embodiment ofthe invention. In an exemplary embodiment of the invention, prosthesis100 comprises a low penetratable shell 110 that is optionally, comprisedfrom a biocompatible silicone, polyurethane or other material as iscommonly used for implants. Shell 110 may comprise a single layer ormultiple layers, wherein some layers may be from one material and othersfrom another. Additionally, shell 110 may be smooth or textured, withvarious patterns. Shell 110 can have areas of varying elasticity. Shell110 can have a different thickness in different areas. Optionally, thematerial of shell 110 may be a combination of several materials.Generally, shell 110 serves as an enclosure for preventing the contentof prosthesis 100 from leaking out. Optionally, shell 110 may beprovided in various shapes, for example round, oval, anatomical, customor other.

In an exemplary embodiment of the invention, gel mixture 120 is producedwith a reduced specific gravity value to reduce the overall weight ofthe prosthesis. In an exemplary embodiment of the invention, gel mixture120 is comprised from a medical grade cohesive silicone gel and reducedspecific gravity particles, for example micro-spheres 140. Optionally,micro-spheres 140 may be provided with any shape and are not necessarilyspherical. Optionally, the cohesive silicone gel is selected frommaterials which are not restricted for use inside the human body,although a low penetratable shell may be sufficient to allow othersilicone gels since the shell prevents contact with the internal body ofthe person. An example of a gel not-restricted for internal use isMed3-6300, which is provided by Nusil technology, Carpintera, Calif.(www.nusil.com). Optionally, Med3-6300 is provided with a specificgravity value of 0.98 g/cc. It should be noted that a cohesive siliconegel generally maintains its form and requires a force to be applied toremove pieces from the gel once it is cured to a final form. In someembodiments of the invention, other types of gel materials may be usedto form the mixture. The basic requirements of the material are toprovide the correct feel, which mimics breast tissue, bio-compatibilityor at least being non-toxic. An example of such a material is Elast-Eon®which is manufactured by AorTech International plc, Surrey, UnitedKingdom.

In an exemplary embodiment of the invention, micro-spheres 140 areformed from plastic, ceramic, silicone, polymethyl methacrylate or glassalthough other materials may be used. Optionally, micro-spheres 140provide a solid filling material which is hollow thus filling arelatively large volume while maintaining a relatively low weight. In anexemplary embodiment of the invention, micro-spheres with a diameterless than 200 microns or even less than 50 microns (e.g. 30-40 microns)are used to form gel mixture 120 in order to minimize any effect ofmicro-spheres 140 on the feel of gel mixture 120.

Micro-spheres are provided by many manufacturers, for example (a)Potters Industries Inc., Valley Forge, Pa., (b) 3M Company, St. Paul,Minn., (c) Sovereign Packaging Group Inc., Buffalo, N.Y. and others.Optionally, micro-spheres 140 provide a filling with a reduced specificgravity, for example “dualite” plastic micro-spheres manufactured bySovereign with an average diameter of 30-40 microns have a specificgravity of 0.1 g/cc. other micro-spheres with similar diameter may beheavier (e.g. glass micro-spheres 0.34 g/cc at Potters) or lighterdepending on the thickness of the surface of the spheres and thematerial used (e.g. glass microspheres K1 0.125 g/cc at 3M with anaverage diameter of 120 microns).

In some embodiments of the invention, the particle used (e.g.micro-spheres 140) may be electrically charged or neutral. They can becoated with a coating to improve adhesion, reduce permeability oraugment other qualities.

In an exemplary embodiment of the invention, micro-spheres 140 areadmixed into the silicone gel with a concentration of less than 60% oreven less than 45% by volume. With 3M K1 spheres and the gel in theexample above this requires less than 9-16% by weight, since one CCweighs approximately an eighth of the weight of the silicone gel.Likewise glass micro-spheres from potters require less than 26-35% byweight. Optionally, a higher concentration by volume would detrimentallyaffect the resilience and feel of the resulting mixture to an extentthat it would be less appropriate for use in prosthesis 100.

In an exemplary embodiment of the invention, micro-spheres 140 areadmixed into the silicone gel at room temperature. Optionally, themixture is agitated to maintain a uniform distribution of micro-spheres140. In an exemplary embodiment of the invention, a catalyst, forexample a platinum catalyst is admixed with the micro-spheres to speedup the curing process, when heat is applied so that the micro-sphereswill not manage to migrate to the surface during the curing thusproviding a substantially uniform gel. Optionally, vacuum deaeration isrecommended during the mixing process to removed trapped air bubbles.Alternatively, pressure may be applied to provide a uniform mixture. Inan exemplary embodiment of the invention, the mixture is heated in anoven with a temperature of between 120° C. to 150° C. for approximatelybetween 5-30 minutes. Optionally, the mixture is then post cured for afew hours (e.g. 4) with a temperature of 200° C. to remove volatilecomponents and other residuals and to provide a full, stable cure.Optionally, other processes may be used to prepare gel mixture 120, forexample using other temperatures ranges and time lengths.

In an exemplary embodiment of the invention, a mixture of 60% by volumeof Med3-6300 silicone gel with 40% by volume 3M K1 micro-spheresprovides a gel mixture 120 with the required resiliency and feel and aspecific gravity of 0.71 g/cc. Optionally, a similar mixture with glassmicro-spheres (manufactured by Potters) provides a gel mixture 120 witha specific gravity of approximately 0.79 g/cc. In some embodiments ofthe invention, glass micro-spheres are preferred over plastic due totheir relatively inert characteristics, bio-compatibility anddurability. In contrast plastic or other material micro-spheres may bepreferred since they are lighter.

Optionally, gel mixture 120 would typically have a resiliencecharacterized by a penetration measurement of approximately, between 4to 150 mm/10 using a penetrometer with a 12 g 1″ diameter shaft over 15seconds.

In an exemplary embodiment of the invention, a desired amount (e.g. 400cc) of gel mixture 120 is enclosed in shell 110 to form a reduced weightimplantable prosthesis. Optionally, as described above a reduction inweight of 25-55 percent is achieved by the use of gel mixture 120instead of the original silicone gel (e.g. Med3-6300). Optionally, shell110 may be provided in various shapes, for example spherical, oval,teardrop/pear (sometimes referred to as anatomical) or custom shape.

In an exemplary embodiment of the invention the outer surface of shell110 is provided with a smooth surface, a rough surface or a coatedsurface or with various textures to induce contact with the internaltissue of the person to secure the position of the implant and toprevent capsular contracture.

In an exemplary embodiment of the invention, the reduced weightprosthesis may be provided in various sizes, for example extending from50 CC to 1500 CC or larger or smaller. Optionally, a reduced weightprosthesis may be implanted in other areas of the body other than thebreast, for example to replace testicles, pectorals, a chin, cheeks, acalf, buttocks or other parts of the human or an animal body, whileexhibiting properties similar to natural tissue. In some embodiments ofthe invention, the reduced weight prosthesis may be constructed forexternal use, for example to be worn under or as part of a person'sclothes. Optionally, a reduced weight prosthesis will be used to replacean existing implant.

In some embodiments of the invention, a weight reduction greater thanthat achieved by the use of gel mixture 120 is desired. Optionally, gelmixture 120 can be used to circumvent a volume in the prosthesis with acontent of even further reduced weight to reduce the overall weight ofthe prosthesis. Optionally, gel mixture 120 will interface shell 110 andprovide the correct feel for the prosthesis, so that the inner volumecan be provided by materials that do not necessarily have the desiredresilient feel.

FIG. 2A is a schematic illustration of a prosthesis 200 with a centeredinner volume 130 with a first filler material and an outer volumeencasing the inner volume with a second filler material (e.g. gelmixture 120), according to an exemplary embodiment of the invention.Optionally, inner volume 130 may be positioned closer to one side ofprosthesis 200, for example attached to shell 110 so that it may bepositioned in the posterior, adjacent to the rib cage of the patientproviding gel mixture 120 in the outer volume to face the anteriorsurface and provide the required resilient feel. FIG. 2B is a schematicillustration of prosthesis 200 with inner volume 130 with a first fillermaterial in a non-centered position, and the outer volume encasing theinner volume with the second filler material (e.g. gel mixture 120),according to an exemplary embodiment of the invention.

FIG. 3A is a schematic illustration of inner volume 130 filled with afoamy like substance 310, according to an exemplary embodiment of theinvention. In some embodiments of the invention, foamy like substance310 may be provided by the use of a silicone foam, for example R-2350provided by Nusil technology or Silastic® sponge system silicone rubbercompound provided by Dow Corning Corp. (www.dowcorning.com). Dow CorningCorp publicizes that it offers spongy silicone prepared by mixingchemical blowing agents into the silicone before curing and also spongysilicone created in a process that uses water as the chemical agent forforming bubbles in the silicone. In an exemplary embodiment of theinvention, foamy like substance 310 serves as a reduced weight fillerfor inner volume 130 due to the gas holes that are spaced throughout thesubstance. Typically foamy like substance 310 such as in the examplesmentioned above, have a specific gravity that is approximately a thirdof the specific gravity of silicone gel. R-2350 has a specific gravityof 0.35 and Silastic® sponge system silicone rubber compound has aspecific gravity of 0.37. In an exemplary embodiment of the invention,by providing an inner volume 130 as a third of the volume of prosthesis200 the weight of prosthesis 200 may be reduced by approximately anadditional 10% in addition to the reduction by using gel mixture 120.Optionally, the total reduction in weight achieved by the embodimentillustrated by FIG. 2B and FIG. 3A with inner volume 130 being a thirdof prosthesis 200 is between 35% to 65%. However a greater weightreduction may be achieved depending on the details described above, forexample the type of micro-spheres used and the size of inner volume 130.In some embodiments of the invention, the size of inner volume 130 maybe a quarter of the volume of prosthesis 200 or less. Alternatively thesize of inner volume 130 may be a half of the volume of prosthesis 200or larger.

In some embodiments of the invention, inner volume 130 is enclosed in ashell, for example similar to shell 110. Alternatively, inner volume 130may be in direct contact with gel mixture 120 and not enclosed in aprotective shell, depending on the filling materials used (e.g. a closedcell foam—does not absorb gel into the cells). Optionally, if gelmixture 120 is able to be absorbed by the filling material of innervolume 130 and cause shrinkage of the overall size of prosthesis 200,inner volume 130 would be enclosed in a protective shell.

In an exemplary embodiment of the invention, a gel mixture withmicro-spheres of a larger diameter (e.g. 500 microns or 1000 microns)can be used to fill inner volume 130. Optionally, such a gel mixture hasa lower specific gravity value, since the micro-spheres consume morespace and have a larger hollow volume. In an exemplary embodiment of theinvention, such a gel mixture may have a specific gravity value as lowas 0.42 g/cc or less.

FIG. 3B is a schematic illustration of inner volume 130 with acompartment like structure 320, according to an exemplary embodiment ofthe invention. Optionally, the filling material for inner volume 130 maybe a silicone material with an orderly structure such as a hollowtrabecular structure or hollow micro-cells. Optionally, such a structurehas a specific gravity of 0.3-0.7 depending on specific geometry. In anexemplary embodiment of the invention, a compartment like structure 320is formed by pouring uncured silicone rubber over a mold consisting ofspherical or cuboidal projections, for example 2 mm high with a volumeof 8 cubic millimeters and spaced 0.5 mm apart. The uncured silicone ispoured to a depth of 2.5 mm and cured. The result is a sheet of 2.5 mmsilicone with cavities open on one side. These sheets are adhesivelyattached together to provide a hollow cellular structure. Optionally,other methods may be used as known in the art

FIG. 3C is a schematic illustration of inner volume 130 with a threedimensional mechanical rod like structure 330, according to an exemplaryembodiment of the invention. Optionally, structure 330 forms a hollowvolume with an encasing shell and rods to keep the shell fromcollapsing. In an exemplary embodiment of the invention, structure 330is formed from a silicone substance using a single mold or multiplemolds and then connected to form a three dimensional structure, asillustrated in FIG. 3C. In some embodiments of the invention, structure330 is enclosed in an enveloping shell 335 to prevent gel mixture 120from permeating into the hollow volume. In an exemplary embodiment ofthe invention, an inner volume 130, which fills a fifth of the volume ofprosthesis 200 using structure 330 provides a total weight reduction ofat least 15% since it is basically a hollow volume.

FIG. 3D is a schematic illustration of inner volume 130 with a selfsupporting surface structure 340, according to an exemplary embodimentof the invention. Structure 340 forms a shell enclosing a hollow volumesimilar to structure 330, however structure 340 in contrast to structure330 is self supporting and does not require rods to maintain its form.

In some embodiments of the invention, the embodiments described abovefor filling inner volume 130 provide an elastic volume filler, which inconjunction with gel mixture 120 provides prosthesis 200 with therequired resilience and feel. Alternatively, the above suggestedembodiments for inner volume 130 provide a relatively less elasticfiller, and gel mixture 120 provides the padding to provide prosthesis200 with the required resilience and feel in spite of inner volume 130.

FIG. 4A is a schematic illustration of a concentric multilayeredprosthesis 400, according to an exemplary embodiment of the invention.In an exemplary embodiment of the invention, prosthesis 400 may comprisea shell 405 and multiple layers and compartments with optionallydifferent types of fillings, for example the innermost layer 430 maycomprise a hollow self supporting shell, the next layer 420 may comprisea foamy filling and the outer layer 410 may be filled with gel mixture120. Alternatively, the layers may be arranged in any other orderoptionally, depending on the properties required for the resultingprosthesis. The compartments may be adjacent to each other or concentricor acentric. The compartments can be of different shapes and sizes.There may be barriers between the compartments or the filler materialsin each compartment may interface gel mixture 120 and/or each otherdirectly. The filler material in each compartment may be different orthe same and a compartment may have more than one filler material. Theboundary between compartments may be an abrupt or a gradual change infiller material properties, density or other characteristics.

In an exemplary embodiment of the invention, prosthesis 400 may comprisemultiple layers and compartments in different shapes. Optionally, ananatomical shaped layer 430 may be located in proximity to the rib cageand constructed from a silicone foam, which is separated by a siliconebarrier from layer 420. Optionally, layer 420 may comprise a gel mixturewith a high concentration of large and small microspheres, for example40% by volume of 120 micron micro-spheres mixed with 15% by volume of 30micron micro-spheres and 45% by volume of silicone gel. Optionally,anterior layer 410 may be filled with a gel mixture of a lowconcentration such as 10% by volume of lightweight small particles with90% by volume silicone gel. Optionally, there may or may not be abarrier (e.g. a shell) between high concentration layer 420 and lowconcentration layer 410. It should be noted that although FIG. 4illustrates three layers or compartments—there may be more than three.

FIG. 4B is a schematic illustration of a prosthesis 450 with multipleinner volumes, according to an exemplary embodiment of the invention. Insome embodiments of the invention, prosthesis 450 may comprise a shell405 and multiple inner volumes (or layers) 410, 420, 430 similar toprosthesis 400. In FIG. 4B the inner volumes are shown placed next toeach other (e.g. 410, 430) or internal to each other (e.g. 420, 430).

In some embodiments of the invention, different layers may be filledwith gel mixtures with different sized micro-spheres. Optionally, themost outer layer comprises gel mixture 120, which provides a feel mostconforming to real breast tissue. Other layers may be harder or lessresilient but may reduce the overall weight of prosthesis 400.

In some embodiments of the invention, gel mixture 120 or other gelmixtures used for filling the prosthesis may comprise micro-spheres ofmultiple diameters. Optionally, the use of micro-spheres of multiplediameters allows better exploitation of the available volume, thusfurther reducing the specific gravity of gel mixture 120.

It should be appreciated that the above described methods and apparatusmay be varied in many ways, including omitting or adding steps, changingthe order of steps and the type of devices used. It should beappreciated that different features may be combined in different ways.In particular, not all the features shown above in a particularembodiment are necessary in every embodiment of the invention. Furthercombinations of the above features are also considered to be within thescope of some embodiments of the invention.

Section headings are provided for assistance in navigation and shouldnot be considered as necessarily limiting the contents of the section.

It will be appreciated by persons skilled in the art that the presentinvention is not limited to what has been particularly shown anddescribed hereinabove. Rather the scope of the present invention isdefined only by the claims, which follow.

1. A reduced weight implantable breast prosthesis, comprising: a unitaryouter surface shell for encapsulating the breast prosthesis; a gelmixture comprising a first gel mixture of a cohesive gel and particlesfor filling the shell; one or more inner volumes internal to the shellwhich do not contain said first gel mixture; wherein the first gelmixture contains less than 60% by volume of particles mixed into saidcohesive gel, wherein said particles are microspheres, wherein at leastone inner volume contains a second gel mixture having a greaterpercentage of microspheres by volume than said first gel mixture,wherein the second gel mixture of said one or more inner volumes has aspecific gravity that is less than the specific gravity of said firstgel mixture; wherein said one or more inner volumes containing thesecond gel mixture are less resilient than said first gel mixture; andwherein the implantable prosthesis is adapted for implantation in thebreast.
 2. A prosthesis according to claim 1, wherein the total volumeof said one or more inner volumes is less than half of the volume of theprosthesis.
 3. A prosthesis according to claim 1, wherein the totalvolume of said one or more inner volumes is less than a third of thevolume of the prosthesis.
 4. A prosthesis according to claim 1, whereinthe total volume of said one or more inner volumes is greater than aquarter of the volume of the prosthesis.
 5. A prosthesis according toclaim 1, wherein said one or more inner volumes are surrounded by saidfirst gel mixture.
 6. A prosthesis according to claim 1, wherein atleast one of said one or more inner volumes is approximately centered insaid outer surface shell.
 7. A prosthesis according to claim 1 whereinat least one of said one or more inner volumes is positioned adjacent toone side of said outer surface shell.
 8. A prosthesis according to claim1, wherein said second gel mixture microspheres have a larger diameterthan the microspheres in the first gel mixture.
 9. A prosthesisaccording to claim 1 wherein at least one of said inner volumes issubdivided to an internal outer layer and an internal inner volume. 10.A prosthesis according to claim 1, wherein said micro-spheres arehollow.
 11. A prosthesis according to claim 1 wherein said first gelmixture comprises microspheres of more than one size.
 12. A prosthesisaccording to claim 1, wherein said outer surface shell is formed from alow penetratable material.
 13. A prosthesis according to claim 1,wherein said first gel mixture masks the feel of the content of said oneor more inner volumes.
 14. A prosthesis according to claim 1 whereinsaid second gel mixture comprises microspheres of more than one size.15. A prosthesis according to claim 1 wherein said outer surface shellhas a smooth outer surface.
 16. A prosthesis according to claim 1,wherein said outer surface shell has a textured outer surface.
 17. Aprosthesis according to claim 1, wherein said outer surface shell isround in shape.
 18. A prosthesis according to claim 1 wherein said outersurface shell is anatomical in shape.
 19. The prosthesis of claim 1,wherein said microspheres are less than about 1000 microns in diameter.20. The prosthesis of claim 19, wherein said microspheres are less thanabout 500 microns in diameter.
 21. The prosthesis of claim 20, whereinsaid microspheres are less than about 200 microns in diameter.
 22. Theprosthesis of claim 1, wherein said microspheres comprise a materialselected from the group consisting of plastic, ceramic, silicone,polymethyl methacrylate and glass.
 23. The prosthesis of claim 1,wherein the specific gravity of said first gel mixture is up to about0.8 g/cc.
 24. The prosthesis of claim 23, wherein the specific gravityof said first gel mixture is up to about 0.4 g/cc.
 25. The prosthesis ofclaim 24, wherein the specific gravity of said first gel mixture is upto about 0.3 g/cc.
 26. The prosthesis of claim 1, wherein a total volumeof the prosthesis is from about 50 cc to about 1500 cc.
 27. A reducedweight implantable prosthesis, comprising: a unitary outer surface shellfor encapsulating the prosthesis; a gel mixture comprising a first gelmixture of a cohesive gel and particles for filling the shell; one ormore inner volumes internal to the shell which do not contain said firstgel mixture; wherein the first gel mixture contains less than 60% byvolume of particles mixed into said cohesive gel, wherein said particlesare microspheres, wherein at least one inner volume contains a secondgel mixture having a greater percentage of microspheres by volume thansaid first gel mixture, wherein the second gel mixture of said one ormore inner volumes has a specific gravity that is less than the specificgravity of said first gel mixture; wherein said one or more innervolumes containing the second gel mixture are less resilient than saidfirst gel mixture; and wherein the prosthesis is adapted forimplantation in a location of a body of a subject selected from thegroup consisting of scrotum, pectoral, chin, cheek, calf and buttock.